//1516
#include <bits/stdc++.h>
using namespace std;
const int N = 1e5+10;
int h1,h2,n,ne[N];
char e[N];
bool st[N];
int main(){
cin >> h1 >> h2 >> n;
while(n--){
int a,c;
char b;
cin >> a >> b >> c;
e[a]=b;
ne[a]=c;
}
for(int i =h1; i != -1;i=ne[i]) st[i]=1; //标记出现过
for(int i =h2; i != -1;i=ne[i]){
if(st[i]){ //再判
printf("%05d",i);
return 0;
}
}
printf("-1");
return 0;
}